Circuit breaker



March 2, 1943. J. A. coY

CIRCUIT BREAKER Filed Oct. 17, 1940 7 Sheets-Sheet 1 INS U I. ATlO/INVENTOR J seph 61303. -B

2 fi arr ys.

March 2, 1943. J. A. COY CIRCUIT BREAKER Filed Oct. 17, 1940 7Sheets-Sheet 3 g A s gwscws lllll lllllillK I llilillinlll lullhfliINVENTOR Joseph H C 03: a WFM nTTjys.

a 7 sheets-sh s; 4 Y

J. A. COY

I; l R. 5 me 6 o J a h a |L J s whvllll 0 W 6 J J? a 0 61 M s a a 6 a ZWW. T wv C'IRCUIT BREAKER Filed Oct. 17, 1940 u D X I. E 9 O m 0 Q m2 6w 4 m M 7X w 0 1 1. 6 W m FEE m s March 2, 1943.

March 2, 1943, A @Y 2,312,753

CIRCUIT BREAKER Filed on. 17, 1940 7 sneaks-sheets INVENT OR.

J se 2k 17. Co

%WWZW March Z,1 943. J. A. -COY 2,312,753

CIRCUIT BREAKER Filed Oct. 17, 1940 7 Sheets-Sheet 6 I (ID GD I Q gINVENT OR.

, 94 69 jiibseph 17. C03. .9 10 y WaM.

7 Sheets-Sheet 7 INVENTOR.

J. A. COY

CIRCUIT BREAKER Filed Oct. 17, 1940 March 2; 1943.

EFF Et I I1 iofikdawil Patented Mar. 2, 1943 CIRCUIT BREAKER Joseph A.Coy, Cincinnati, Ohio, assignor to The Wadsworth Electric ManufacturingCompany, Inc., Covington, Ky., a corporation of Kentucky ApplicationOctober 17, 1940, Serial No. 361,611

10 Claims.

The present invention relates to circuit breakers.

An object of the invention is to provide a circuit breaker which isresponsive to extremely small current variations in the circuit which isprotected thereby.

Another object of the invention is to provide a breaker which isadaptable to a great number of electrical wiring systems withoutrequiring a structural change.

A further object of the invention is to provide a circuit breaker whichis responsive to current conditions in either leg of a circuit protectedby said breaker, or which may be made responsive to current conditionsin a plurality of circuits protected by the breaker. In the latter casean overload condition in any one circuit protected by the breaker willcause said breaker to rupture all of said protected circuits.

A still further object of the invention is to provide a novel actuatingmember for a circuit breaker which is adapted to control and coordinatethe movement of a plurality of circuit contact bridges.

Another object of the invention is to provide vices, all said devicesmove to automatically open the protected circuit or circuits.

Another object of the invention is to provide a simple, eflicient andcompact circuit breaker for accomplishing the above objects.

Other objects Will be apparent from the following specification anddrawings, in which:

Fig. 1 is a perspective view of my circuit breaker.

Fig. 2 is an enlarged cross-sectional view taken on line 2-2 of Fig. 1.

Fig. 3 is an enlarged cross-sectional view taken on line 3-3 of Fig. 2'.

Fig. 4 is an enlarged, cross-sectional view taken through thelongitudinal center of the circuit breaker.

.Fig. 5 is a side elevational view of the breaker with the front sidewall removed.

.Fig. 6 is a fragmental cross-sectional view taken on line 66 of Fig. 5.Fig. 7 is a fragmental side elevational view of a modified means foractuating the collapsible means by the opposed solenoids for the breakerillustrated in Figs. 16.

Fig. 8 is a view taken on line 88 of Fig. 7.

Fig. 9 is a side elevational view Ofiia modifica- Cir tion of my breakerwith the cover and sides of the casing removed.

Fig. 10 is a view taken of line Ill-l0 of Fig. 9.

Fig. 11 is a modification of the breaker illustrated in Figs. 9 and 10.

Fig. 12 is a view taken on line 12-42 of Fig. 11.

One embodiment of my invention is illustrated in Figs. 1 to 6 andcomprises a casing having a base l5 made of electrical insulatingmaterial. The base is substantially rectangular in plan view and isprovided at each end with centrally disposed exterior recesses l6 andI1, said base having perforated fastening projections i8 extendingtherefrom and disposed at the bottom of the recesses. The casing alsohas a cover l9 which rests upon the base l5 and consists of a top andend walls 2| and 22, said end walls being provided with recesses 23 and24 in vertical alignment with the recesses I6 and I! respectively,formed in the base. The cover [9 is secured to the base by means of arear side wall 25 and a front side wall 26 which completes the casingmember and engages the front and rear edges of the cover [9 and is incontact with the front and rear sides of the base [5, a plurality oftransverse rivets 2'1 being provided to fasten the cover and the base tothe front and rear side walls. The cover is also provided with cut-outportions 28 at the four corners thereof so as to expose the four cornersof the base upon which the terminals of the conducting strips rest. Asshown in Fig. 1, the manual switch lever and binding post terminals arethe only breaker mechanism which appear exteriorly of the casing.

As shown in Figs. 2, 3 and 4, the base is pro vided with upstanding endprojections 29 and 30 which are connected by means of a centrallydisposed platform 3| extending longitudinally of the base inlongitudinal alignment with recess portions 16 and I! of said base.

Devices responsive to current conditions in the circuit take the form ofsolenoids 32 and 33 which are mounted in adjacent relationship on thebase by means of U-shaped frames 36. The frames rest in transversedepressions 35 formed in the platform and are fastened to said base bymeans of screws 35 countersunk in the base (Fig. 4). Insulating material31 is interposed between the solenoid coils and the frames whilst theexterior of said frames is electrically insulated by sheet material 38.

As shown in Figs. 2 and 3, one end 39 of the coil of solenoid 32 isfastened to conductor strip 40 which has a'screw 4! at its exposed endwhich serves as a binding post for one leg of a circuit to be protected.The other end of the solenoid coil is fastened to a conducting strip 42which carries at its free end a contact 63. Another contact 44 ispositioned adjacent contact 43 and said contacts constitute a pair ofcontacts forming a gap in the leg of the circuit in which they areinterposed. Contact 44 is fastened to the free end of a conductor strip45which terminates exteriorly of the casing and at that end is providedwith a screw 45 which is a binding post for the leg of said circuit.

Another leg of a circuit passes through the opposed longitudinal side ofthe base in a similar but reverse manner. As shown in Figs. 2 and 4, thecircuit responsive device for solenoid '33 has with the block and whichextend diametrically from the side of the block and are positioned in avertical plane disposed intermediate two contacts constituting the pairof stationary contacts. The arms are adapted to move in opentopped slotsformed in the platform, as indicated at 60 in Figs. 3 and 6. The ends ofthe arms are received in vertical guides 61 and 62 formed in the rearand front side walls of the casing, respectively (Figs. 1 and 2). Theupper extremity of these guides limits the upper or open contactposition of the actuating means which also determines the open contactposition of the bridges one end of its coil fastened to a conductorstrip 41 provided with an exposed binding screw 48, whilst the other endof the coil is fastened to a conductor strip 49 provided at its innerend with a contact 50. Contact 5|, constituting with contact 50 a pairof stationary contacts, is fastened to the end of conductor strip 52providedat its exposed end with a binding screw 53. The pairs ofstationary contacts 4344 and 53-5! are closed by means of movablecontact bridges 54 and 55, respectively, which are in vertical alignmentwith said stationary contacts and are provided, when actuated, with avertical rectilinear movement.

When the contact bridges are in closed contact position, the electricalcircuit through the breaker is as follows:

A wire serving as one leg of a circuit is fastened to the binding post4| and-current passes through conductor strip 48, solenoid coil 32,conductor strip 42, contact 43, bridge 54, contact 44, conductor strip45, binding screw 46; another leg of a circuit engages the conductorstrip 4'1, the current passing through solenoid 33, conductor strip 49,contact 55, bridge 55, contact 5!, conductor strip 52. The two circuitsthrough the circuit breaker, outlined above, may constitute both legs ofa circuit leading to a translator device, in which case the bindingscrews lll and-53 would be fastened to the line-side of said'legs,whilst the bindingscrews and 43 would be fastened to the load side ofthe circuit serving said device. The breaker may also be used to protecttwo separate circuits by wiring one leg of each circuit through oneside-of the breaker. The breaker may also beused for three-phasecircuits, as may readilybe understood by those skilled in the art.

A strip of insulating board 545 is positioned upon the conductor stripsfor eachside of the breaker, said insulating material extending from thebottom edges of the insulating material 38 and covering the transversearea from the platform 3| to the side walls of the casing. Theinsulating board-is provided with a cut-out portion 54| which permitsthe pairs of stationary contacts to extend upwardly therefrom forcontact with the movable bridges 54.

The actuating means for coordinating the movement of the plurality ofbridges consists of a cylindrical hollow block 55 which moves in a well51 formed centrally in the platform 3! of the base. It will be notedthat-the block is guided in the well for rectilinear, axial movement,said well beingpositioned so that the axis of the block is centered withrespect to the pairs of stationary contacts. As shown in Figs. 2, 3 and5, the block is provided with horizontal arms 58 and 59 which arepreferably made integrat 54 and which are mounted transversely on theend portions of the arms. The cylindrical block has a web 53 formedhorizontally across the interior thereof, the web being provided with acentral aperture for receiving a rod 64.

The means for biasing the actuating means to open contact positioncomprises a coil spring which encircles the lower end of the'rod 64 andbears against the bottom surface of the web 63 and the bottom of thewell 5?. The block is moved to circuit closed position against theaction of the spring 55 by means of a resilient connection between therod 64 and the block, said connection comprising a shoulder 66 formed atthe upper end of the rod and a coil spring 61 which encircles the rodand bears against the upper surface of the web and the shoulder 66.

A manual operating means isprovided for controlling the movement of theactuating means which takes the form of a lever 68 having a circularbody portion and rotatably mounted on the casing by means of a pin 69which is journalled at its ends in spaced ears 73 depending from the topof the casing cover I9. As shown in Fig.4, the circular portion of thelever has a hollow annular center H and a slot 12 formed in the rim ofthe circular portion to provide clearance for the collapsible means.

The collapsible means connecting thesaid operating means to theactuating meanscomprises a toggle element having a link 13 pivoted tothe operating means by pin 14 and at its lowerend pivotally fastened toa link '55 by meansof a pin #66. The link 75 is U-shaped in plan (Fig.6) at its upper end to form a shoulder .75 which, when engaged by link75, places the links 13 and 75 over dead center with respect to theirconnec tions with the operating means and the actuating means. The lowerend of link 'ij5-is connected to the shoulder portion E5 of the rod514by means of a pin ll. As shown in Fig. 4, a coil spring 18 has one ofits arms 19 extending into the body portion of the operating means,whilst the other arm extends downwardly and is fastened to the shoulder16 of link 15. The tendency of this spring is to constantly urge theoperating means clockwise to open circuit position (Fig. 4) whilsturging the toggle element to over.center position. The slot 5| formed inthe top; of the casing serves as a stop for limiting thepositions of themanually operating means.

The armatures 82 and 83 for the. solenoids 3| and 33, respectively, arefastened together by means of a bar 34, said bar being connected tocut-out portions in saidarmatures by means of screws 85. The meansonlthe-bar for engaging the collapsible means atits .jointed portion 16comprises a lug 86. The collapsible means, as shown in Fig. 6, is in thepath of movement of the lug 86 when the solenoid is actuated.Thearmatures of the solenoids are biased-to-the position indicated inFigs. 1 to 6 bymeans of a compression spring 81 which bears against theend Wall of the casing cover and the armature 82, the stop for saidarmatures being the side of the casing cover against which the armature83 is urged.

A sheet of insulating material 810 having an inverted U-shaped formencloses the collapsible means and is provided with openings 8' in thevertical side walls thereof to allow the armatures of the solenoids andthe bar 84 connecting them to pass therethrough. The lower ends of thevertical sides of the material are in contact with v the top and sidesof the platform 3| and also the transverse portion of the insulatingmaterial 540. As shown in Fig. 6, insulating panels 812 are positionedagainst the side walls of the casing and are adapted to close off thelongitudinal edges of the U-shaped insulating material 815.

In operation, when an overload condition occurs in one or both of thecircuit legs in which solenoids 32 or 33 are interposed, the armatures82 and 83 will center themselves with respect to the solenoid coilsagainst the action of the compression spring 87 and thus move the lug 85to a position indicated by dotted lines in Fig. 4. In this position lug85 will collapse and thereby render ineffectual the toggle element ofthe collapsible means, thus throwing the operating means, the actuatingmeans and the collapsible means to a position indicated in dotted linesin Fig. 4. The latter position is taken by the parts to the positionindicated in Fig. 4 after actuation of the lug 85 because, as soon asthe toggle joint is broken, spring I8 moves the manually operating meansclockwise to its dotted line position while the spring 65 in the wellmoves the block 56 upwardly to its dotted line position to open thecircuit. The lower arm 80 of the spring I8 tends to urge the togglejoint after it has been broken to its straight line over center positionand said joint will therefore take up that position indicated in dottedlines in Fig. 4. To reset the breaker, it is only necessary to move theoperating means from its dotted line position to the full line positionshown in Fig. 4.

I alSo contemplate modifying my breaker so that the armatures of thecircuit responsive devices 32 and 33 may independently actuate thecollapsible means to open either circuit leg running through my breaker.In this respect, Figs. 7 and 8 illustrate a form of the modification(like numerals refer tosimilar parts in the drawings) wherein armature82 of the solenoid 32 is provided with a short bar'BBhaving a flatshelflike portion 89 formed at its outer end atright angles to said barin longitudinal alignment with the toggle joint of the collapsiblemeans. A vertical support 95) extends upwardly from the base I andslidably engages the under side of the shelf 89. The armature 83 of thesolenoid 33 has a short bar 9I connected thereto which at its outer endis provided with a right-angled shoulder portion 92 which rests on theshelf 89. A compresssion spring 81 for urging the armature 82 to therighthand side of Fig. 7 is provided while tension spring 93 biases thearmature 83 in a direction to the right in said figure. It willtherefore be seen that upon actuation of the armature 82 or armature 83,they will move against the action of the springs associated therewith toindependently trip the toggle joint and open both circuit legs runningthrough the breaker illustrated in Figs. 16, inclusive.

In Figs. 9 and 10 there is illustrated a modification of my breakeremploying a bi-metal instead'of a solenoid as themeans responsive tocurrent conditions in a circuit. In this form the base and the casingtherefore remain substantially the same as the base shown in Figs. 1 to7, inclusive. (Like reference numerals refer to similar parts.)Conductor strip 94 has a binding screw 95 at one end and has one of apair of stationary contacts 96 at its other end. The strip is fastenedto the base I5 by means of a screw 91. The other stationary contact,constituting the pair, is indicated by numeral 98, said contact beingfastened at the end of a conductor strip 99, which contact is fastenedto the base by a screw I08. This conductor strip 99 is in electricalcontact with a foot portion of an inverted U-shaped bimetal element lllIwhile the free leg of the bi-metal element is electrically connected toa conducting strip I02 having a binding screw I03 at its outer end. Asillustrated, the electrical contact for the legs of the bi-metalelements are screws I04 which are threaded through the strips and thefeet portions of the bi-metal element and into the base I5. The otherleg of a circuit through the breaker is similar to that just describedand consists of a conducting strip I05 provided at its inner end with astationary contact. A strip I36 is also provided with a stationarycontact which constitutes a pair of stationary contacts and iselectrically connected to one leg of an inverted U-shaped bi-metalelement IIlI by means of a screw I08. The other foot of the bi-metal isconnected to a conductor strip I09 by means of a screw I III.

The upper ends of the bi-metal elements are connected by a rectangularframe I I I ,the opposed parallel sides of the frame being connected tothe bi-rnetal elements by means of rivets Il2. A transverse rod I I 3supported by opposite longitudinal sides of the frame is positioned inalignment with the toggle joint between the links 13 and I5 and isadapted to be moved toward said joint when overload conditions in eitheror both circuit legs through the breaker deflect the bimetal elements.This movement of the rod H3 toward the toggle joint moves said jointbeyond dead center thereby collapsing said joint and permitting thebridges 54 and 55 to move upwardly under the control of the actuatingmeans located in the well 51 of the platform 3i. The structure of theactuating means is similar to that shown in Figs. 1 to 6.

Figs. 11 and 12 show a modification of the bimetal circuit responsivemeans shown in Figs. 9 and 10. (Reference numerals used indicate similarparts.) The structure in Figs. 11 and 12 is similar to that in Figs. 9and 10, except that the means connecting the upper ends of the bimetalsIOI and I0? is modified so that each bi-metal may act independently ofthe movement of the other upon the toggle joint. In this respect,bi-metal IE1! is provided with a U-shaped frame H4 which is fastened atits transverse portion H5 to the upper end of the bi-metal by means of ascrew H6. The ends of the link portions of said frame are turned atright angles inwardly, said portion I ll upon deflection of the bi-metalengaging the toggle joint, whilst the other portion II8 of the frame isprovided with an aperture II9 therein for receiving the free end of arod I20 fastened by screw I2I to the upper end of bi-metal IUI. The freeend of the rod I21} is in a longitudinal position to contact the togglejoint when bi-metal I2I is deflected. It will therefore be understoodthat either bimetal'IOI or IIIIma-y independently break the togglejoint, .thus opening both circuit legs running through the breaker.

What is claimed is: I

1. In a circuit breaker the combination of a base, a number of pairs ofstationary contacts on the base, a contact bridge for engaging each pairof stationary contacts, and adapted to engage and disengage saidstationary contacts, a well formed in the base and disposed between thepairs of stationary contacts, an actuating means comprising acylindricalblock guided for rectilinear, axial movement in the well,horizontal arms extending diametrically from the side of the block andpositioned in a vertical plane disposed intermediate two contactsconstituting a pair of stationary contacts, and a horizontal contactbridge extending transversely from the end portion of each arm and invertical alignment witha pair of stationary contacts, means forbiasingthe actuating means to contact disengaged position, a manuallyoperating means, a collapsible means connected to the operating meansand resiliently engaging the block, and normally adapted to hold theactuating means in contact engaged position, and means responsive tocurrent conditions in the circuit for acting on the collapsible meansand rendering said means inefiective to hold the actuating means incontact engaged position.

2. In a circuit breaker the combination of a base, a casing having atopand side walls fastened to the base, a number of pairs of stationarycontacts on the base, a contact bridge for engaging each pair ofstationary contacts, and adapted to engage and disengage the stationarycontacts, a well formed in the base and disposed between the pairs ofstationary contacts, an actuating means comprising a cylindrical blockguided for rectilinear, axial movement in the well, horizontal armsextending diametrically from the side of the block and positioned in avertical plane disposed intermediate two contacts constituting a pair ofstationary contacts, and a horizontal contact bridge extendingtransversely fromrthe end portion of each arm and in vertical alignmentwith 'a pair of stationary contacts, verticalguides in opposed sidewalls of the casing for receiving the ,ends of the arms, said guidesacting as stops for determining the contact disengaged position of theactuating means, means for biasing the actuating means to contactdisengagedposition, a manually operating means, a collapsible means,connected to the operating means and resiliently engaging the block, andnormally adapted to hold the actuating means in contact engagedposition, and means responsive to current conditions in the circuit foracting on the collapsible means and rendering said means inefiective tohold the actuating means in contact engaged position whereby saidactuating means is moved under the influence of its bias to' contactdisengaged position.

3. A circuit breaker, as set forth in claim 2, wherein the resilientconnection between the block and the collapsible means constitutes ahollow block, a rod fastened to the collapsible means and disposedaxially through the block, said rod having a shoulder thereon, a webportion extending across theinterior of the'block and having an aperturecentrally therein for receiving the rod, and coil spring encircling therod and engaging the shoulder and the web.

4. A circuit breaker, as set forth in claim 2, wherein the means forbiasing the actuating means to contact disengaged position comprises ahollow cylindrical block provided interiorly with a web portion, and acoil 'springdisposed within the block and bearing against the bottom ofthe well and the'web portion of theblock.

5. In a circuit breaker the combination of a base, circuit responsivedevices mounted in ad'- jacent relationship on the base, each responsivedevice adapted tobe interposed in a leg of a circuit, pairs ofstationary contacts mounted on the base and each pair adapted ,to be ina leg'of a circuit,'movable contact bridges each adapted to engage anddisengage 'a pair of stationary contacts, a collapsible meansengagingthe contact bridges and positioned .between' the circuitresponsive devices for holding said bridges in contact engagedpositions, means for biasing the collapsible meansto contact disengagedposition, and means fastened to the movable part of each circuitresponsive 'device for tripping the collapsible means when an overload;occurs in a leg of a circuit in which saiddevice islinterposed tothereby render the collapsible mjeans ineifective to hold the bridges incontact engaged positions thus permitting all. of said bridges to moveunder theinfluence of the biasing means to contact disengaged positions.

6. In a circuitbreaker the combination of a base, circuit responsivedevices mounted in adjacent relationship o'nthe base, each responsivedevice adapted to beinterposed in a leg of a circuit, pairs of spaced,stationary contacts mounted on the base and each adapted to be in a legof a circuit, a movable contact bridge adapted to engage and disengageeach pair of stationary contacts, collapsible means engaging the contactbridges and positioned between the circuit 'responsive devices forholding said bridges in contact engaged positions, m'eansfor biasing thecollapsible means to contact disengaged position, and anarm fastened tothe movable part of each of the circuit responsive devices for trippingthe collapsible means when an overload occurs in a leg of a circuit inwhich a circuit responsive device is interposed to thereby render thecollapsible means ineffective to hold the bridges in contact engagedpositions thus'permitting all of said bridges to move underthe influenceof the biasing means to contact disengaged positions.

.77. In a circuit breaker the-combination of a base, circuit responsivedevices mounted in adjacent relationship on the base, each responsivedevice adapted to be interposed in aleg of a circuitg'pairs of spaced,stationarycontacts mounted on the base andeach pair adapted to be in aleg of a circuit, movable contact bridgesadapted to engage and disengagethe pairs of stationary contacts, collapsible means engaging the contactbridges and positioned between the circuit responsive devices forholding said bridges in contact engaged positions, means for biasing thecollapsible means to contact disengaged position, a bar fastened to themovable part of the circuit responsive devices, and means on the bar fortripping the collapsible means when an overload occurs in a leg of acircuit in which a circuit responsive device is interposed to therebyrender the collapsible means ineffective to hold the bridges in contactengaged positions thus permitting all of said bridges to move under theinfluence of the biasing means to contact disengaged positions.

8. In a circuit breaker the combination of a base, circuit responsivedevices mounted in adjacent relationship on the base, each responsivedevice adapted to be interposed in a'leg of a circult, pairs of spaced,stationary contacts mounted on the base and each pair adapted to be in aleg of a circuit, movable contact bridges adapted to engage anddisengage the pairs of stationary contacts, collapsible means engagingthe contact bridges and positioned between the circuit responsivedevices for holding said bridges in contact engaged positions, means forbiasing the collapsible means to contact disengaged position, a linkingmember fastened to the movable part of each circuit responsive device,and a lug on the member for tripping the collapsible means when anoverload occurs in a leg of a circuit in which a circuit responsivedevice is interposed to thereby render the collapsible means ineffectiveto hold the bridges in contact engaged positions thus permitting all ofsaid bridges to move under the influence of the biasing means to contactdisengaged positions.

9. In a circuit breaker the combination of a base, circuit responsivedevices mounted in adjacent relationship on the base, each responsivedevice adapted to be interposed in a leg of a circuit, a linking memberfastened to the movable part of each circuit responsive device forcoordinating the movement of said devices in a common plane, acollapsible means positioned adjacent the linking member andintermediate the devices, arms extending from the collapsible means atright angles to the plane of movement of the linking member, pairs ofspaced, stationary contacts mounted on the base and each pair adapted tobe in a leg of a circuit, a contact bridge fastened centrally on eacharm and adapted to engage and disengage a pair of stationary contacts,means for biasing the collapsible means to contact disengaged position,an operating means for holding the collapsible means in contact engagedposition against the action of the biasing means, and means on thelinking member for tripping the collapsible means when an overloadoccurs in a leg or" a circuit to thereby render the collapsible meansineffective to hold the bridges in contact engaged positions thuspermitting all of said bridges to move under the influence of thebiasing means to their contact disengaged positions.

10. In a circuit breaker the combination of a base, circuit responsivedevices mounted in adjacent relationship on the base, each responsivedevice adapted to be interposed in a leg of a circuit, a linking memberfastened to the movable part of each circuit responsive device forcoordinating the movement of said devices in a common plane, acollapsible means positioned adjacent the linking member andintermediate the devices, arms extending from the collapsible means atright angles to the plane of movement of the linking member, pairs ofspaced, stationary contacts mounted on the base and each pair adapted tobe in a leg of a circuit, a contact bridge fastened centrally on eacharm and adapted to engage and disengage a pair of stationary contacts,means for biasing the collapsible means to contact disengaged position,an operating means for holding the collapsible means in contact engagedposition against the action of the biasing means, means for biasing theoperating means to contact disengaged position, and means on the linkingmember for tripping the collapsible means when an overload occurs in aleg of a circult to thereby render the collapsible means ineffective tohold the bridges in contact engaged positions thus permitting all ofsaid bridges and the operating means to move under the influence oftheir respective biasing means to contact disengaged positions.

JOSEPH A. COY.

